High potency animal feeds, as they are normally used today in intensive animal raising, contain a number of additives of prophylactic and/or nutritive effect. These include among others anitbiotics and enzymes. While the use of antibiotics has found acceptance in mixed feeds of all kinds, enzymes are not as yet used on a large scale in the field.
The feed mixtures used in modern intensive animal raising programs are generally optimized in all nutrient components to the extent that further improvement does not seem readily possible.
Thus, U.S. Pat. No. 3,017,272 suggests the use of from 1 to 200 ppm of Virginiamycin in feeds; U.S. Pat. No. 2,809,892 suggests the use of from 1 to 25 ppm of zinc Bacitracin in feeds; U.S. Pat. No. 4,062,732 suggests the use of certain acid proteases in feed, and U.S. Pat. No. 3,455,696 suggests the use of procain penicillin, dehydrostreptomycin or tetracycline and an adic protease in feeds.
United States Patent Applications Ser. No. 814,047 and 814,048, both filed on July 8, 1977, and Ser. No. 952,410, filed Oct. 18, 1978, relate to the discovery of animal food mixtures based on carbohydrates, proteins, fats and, in any given case, the usual kinds of additives, whose nutrient value is optimized through the addition of 5 to 150 ppm of the antibiotics Virginiamycin, zinc Bacitracin or flavophospholipol and of proteolytic enzymes in such an amount that the enzymatic activity is from 0.05 to 2.5 mTU/gm of said animal food mixture. These animal food mixtures result in higher yields with respect to their feed utilization and/or the weight increase produced by them than those obtained using conventional high-potency animal feeds, which contain only antibiotics or enzymes by themselves.